The search for extraterrestrial intelligence, better known as SETI, is taking advantage of a widening array of strategies — ranging from sophisticated laser searches, to a new type of wide-angle optical observatory, to arrangements to conduct the search simultaneously with other scientific efforts.
But new technologies are also bringing new challenges: For example, how will radio astronomers deal with the noise created by a fast-growing number of satellites in low Earth orbit?
The technological pluses and minuses for the SETI quest, and for other strategies aimed at detecting life beyond our solar system, took the spotlight in Seattle last weekend during a session presented at the annual meeting of the American Association for the Advancement of Science.
“We’re bringing a Silicon Valley approach to the search for advanced life,” said Andrew Siemion, who’s the director of the Berkeley SETI Research Center as well as principal investigator for the 10-year, $100 million Breakthrough Listen project. “Usually I add that we’re trying to bring the good parts of Silicon Valley to the search, not necessarily some of the bad parts.”
Siemion focused on the good parts, including the public release of the second big batch of radio data from Breakthrough Listen. That campaign got its start nearly five years ago with a high-profile kickoff from Israeli-Russian tech billionaire Yuri Milner and the late British physicist Stephen Hawking.
Since then, Breakthrough Listen has forged partnerships with radio telescope arrays around the world — most recently with the National Radio Astronomy Observatory’s Karl G. Jansky Very Large Array, which took a star turn in the SETI movie “Contact.”
“We’re developing a system that will allow us to tap all of the data that the VLA produces and use it 24 hours a day, seven days a week to search for anomalies alongside other science,” Siemion said.
If NRAO wins the go-ahead for a next-generation upgrade of the Jansky VLA, Breakthrough LIsten’s capability would be similarly upgraded.
“This is the first radio telescope that would ever be built that would allow us to be sensitive to leakage radiation — radio signals that are as weak as our isotropic emissions from the planet — from a handful of nearby stars,” Siemion said. In other words, it would theoretically be capable of picking up the signals coming from E.T.’s smartphone on Proxima Centauri b.
Huge radio dishes aren’t the only instruments being used in the hunt for alien signals: Pioneer SETI astronomer Jill Tarter touted the development of a new type of wide-angle optical observatory, known as Panoramic SETI or PANOSETI, which would be capable of recording brief flashes of light. Such flashes may be associated with weird phenomena known as fast radio bursts, and there’s a chance they might follow a pattern suggestive of intentional transmissions from a far-off civilization.
Two prototype PANOSETI telescopes are being tested at the Lick Observatory’s Astrograph Dome in California. The plan calls for building two PANOSETI observatories, each with 80 telescopes arranged to cover the sky. “If you get a pulse somewhere between a nanosecond and a second in duration, both observatories will see it, and you will be very confident of your result,” Tarter explained.
Another long-running project at the SETI Institute, called LaserSETI, takes a different approach to the search for optical signals. LaserSETI’s compact camera enclosures are designed to scan the entire sky for short blips of laser light, from as many as 15 sites around the world.
“Since last August, the first two enclosures have been operating on the rooftop of the Robert Ferguson Observatory in Sonoma, California,” Tarter said. “The next two enclosures are going to be placed in Hawaii, at the Haleakala Observatory. And ultimately, we’ll have something like this globally to look at all the sky, all the time, for transients.”
Optical SETI could widen the search for alien signals to a whole new region of the electromagnetic spectrum, but there’s an all-too-earthly obstacle to overcome.
“Neither PANOSETI nor LaserSETI are fully funded, so we can’t say when they might be complete,” Tarter told the Seattle audience. “If you have an opportunity to provide some funding, both of those projects would benefit from it.”
As the acronym suggests, SETI looks for the characteristic patterns of intentional signals from beyond the solar system. But there’s growing interest in the search for signs of less advanced life among the stars.
“We’re not looking for little green men, we’re looking for little green pond slime,” said University of Washington astronomer Victoria Meadows, who heads UW’s Virtual Planetary Laboratory.
In the decade ahead, NASA’s James Webb Space Telescope could track down the first chemical signals of extraterrestrial life processes, perhaps through the detection of such gases as water vapor, methane and carbon dioxide in alien atmospheres. The next generation of ground-based telescopes could also contribute to the quest.
For now, the most promising nearby target for closer inspection is the TRAPPIST-1 system, which appears to have more than one potentially habitable planet. But Meadows warned that appearances can be deceiving. Computer simulations suggest that some seemingly habitable planets could have had their oceans cooked away early in the process of planetary evolution. Such planets turn out looking more like hellish Venus than habitable Earth.
“If you think of the Earth as a kernel of corn, then Venus is like the popcorn of the solar system. … Can we discriminate between a nice habitable planet, and one that’s undergone ocean or atmospheric loss to be in the popcorn zone?” Meadows said.
She said it’s likely to take more than the James Webb Space Telescope to nail down the chemical case for life beyond the solar system.
“JWST will really give us a tantalizing glimpse that would be potentially habitable. … We’ll get this tantalizing glimpse, but we won’t get anything really definitive,” Meadows said. “To do that, we are going to need far more capable missions, and happily, NASA is currently considering them.”
Several mission concepts with implications for astrobiology — including HabEx, LUVOIR, Lynx and Origins — are due to be assessed during a decadal survey of astronomical priorities.
Over the course of the next couple of decades, those new spacecraft should give astronomers a much better view of the heavens. But other types of new spacecraft are giving astronomers pause: Several companies — including SpaceX, OneWeb, Telesat and Amazon — are planning to put thousands of satellites in low Earth orbit to provide global broadband internet access. The satellites already launched by OneWeb and SpaceX have sparked concerns about radio interference, an issue that strikes at the heart of the traditional SETI quest.
“If it happened that some civilization is transmitting in exactly one of the frequencies used by one of these companies, there’s going to be a problem detecting it,” NRAO Director Tony Beasley told GeekWire.
Beasley said he and other astronomers are involved in discussions with SpaceX to work out ways to minimize the potential harm, and he’s hoping to have similar talks with OneWeb and the other satellite constellation companies. One of the measures being discussed would involve switching off the satellites for brief periods while they pass over sensitive radio dishes. Other measures could involve processing radio data to cancel out the satellites’ effects.
“There are ways with our telescopes to be able to detect nearby moving objects … and so we do have ways to separate them from celestial signals in some sense,” Beasley said. “But in general, a noisier environment just makes it harder to hear something.”
If scientists do hear a confirmed signal from E.T., you can bet that the conflict over constellations would quickly fade away. So would the financial challenges that SETI astronomers currently face.
“I’ve been promised unlimited funding if we detect a signal,” Breakthrough Listen’s Siemion said.